1. Related Application
The present application claims the benefit of co-pending U.S. provisional pat. App. Ser. No. 61/296,604, filed Jan. 20, 2010, the contents of which are incorporated herein by reference in their entirety.
2. Field of the Invention
The present invention relates generally to connectors which can be mated and unmated in very harsh environments, such as underwater, and is particularly concerned with a harsh environment electrical connector.
3. Related Art
There are many known electrical rotary joint connectors which function in dry environments, but not many that are suitable for harsh or underwater environments. Harsh environment rotary joint connectors are currently in use only for limited applications, such as down-hole drill strings, but they are not intended for general use, or for mating while completely submerged in a hostile environment.
Most current underwater connectors designed for mating while completely submerged need to have the plug and receptacle contact parts keyed into rotational alignment for mating. The earliest underwater connector was a rubber-bodied pin-and-socket connector that embodied one or more ring-like contacts molded into a cylindrical rubber pin, and respective one-or-more ring-like contacts molded into a rubber bore, which required no particular rotational alignment. For that reason, such connectors are said to be keyless. Although inexpensive, such connectors are not reliable enough for most critical applications. They have the distinct disadvantage that they cannot be unmated underwater except at very modest depths; and, in models having more than one set of contacts arranged along the pin and bore, cross-connection briefly takes place as un-matched pin and socket contacts slide past each other during mating and de-mating. Cross-connecting circuits can sometimes be disastrous for the electronics to which they are attached.
The offshore oil and gas industry is one of the principal markets for underwater mateable connectors. Many of the connectors used for that industry's subsea operations are connected and disconnected remotely, either by being mounted to large, opposed plates (stab plates) that come together during the mating process to join arrays of connectors, hydraulic couplers, and the like, or by the manipulators of remotely operated vehicles (ROV's). Mating remotely is made more difficult and expensive by the requirement to control the rotational alignment of the individual components to be mated.
Two-contact fluid-filled electrical connectors that required no rotational alignment were made commercially available in the early 1980s. One example of such a connector is described in U.S. Pat. No. 4,606,603 of Cairns. These connectors did solve the rotational alignment problem, but one problem with such connectors was that two contacts were not enough to satisfy the needs of most operations. Another problem was that the receptacle's circular end-opening, which had to be pinched tightly closed before and after mating, had to be stretched several hundred percent to receive the plug's pin. If mated for a long time, particularly at low ocean temperatures, the opening did not close upon de-mating, and the connector subsequently failed.
In the late 1980's, multiple pin, fluid-filled connectors were once again introduced. They have all the required barriers, are robust, and exceptionally reliable. One such connector is the subject of U.S. Pat. No. 4,948,377 of Cairns. These connectors are manufactured by Teledyne ODI of Daytona Beach, Fla. They replaced the two-contact, single pin fluid-filled connectors described above as the high-reliability standard for the offshore industry. These connectors still have the rotational alignment problem, however, which somewhat limits their use, and requires special keying provisions for rotational alignment.
In the early 1990's a keyless, coaxial, oil-filled, wet-mateable connector was introduced that required no rotational alignment. This connector is described in U.S. Pat. No. 5,171,158 of Cairns (hereinafter '158 patent). It consisted of multiple ring-like contacts spaced along a constant diameter portion of the plug pin. The receptacle had corresponding ring-like contacts spaced along a rubber bore to receive the plug contacts. The overall layout of the contacts was very similar to the first type of connector described above. The main differences were that the connector of the '158 patent housed the receptacle contacts in a pressure-balanced, fluid-filled chamber; and, when mated, the individual pin/socket pairs were separated from each other by a single rubber seal. Unlike the coaxial connector of U.S. Pat. No. 4,606,603 (hereinafter '603 patent), the anterior sealed opening through which the plug's probe passed when entering the receptacle's chamber was occupied by a spring loaded piston before and after mating. That removed the necessity of the sealed opening to be pinched closed to a zero diameter as in the '603 patent.
The connector shown in the '158 patent was reasonably successful technically and quickly gained a dedicated customer base, but it was discontinued after being on the market for just a couple of years. It proved to be too expensive and difficult to manufacture. It also still had the problem of cross-connection during mating and de-mating as the plug's contacts wiped across receptacle contacts which were not their intended counterparts.
Thus, underwater connectors today typically require rotational alignment or keying for connection underwater. Such connectors cannot be used to connect pieces of equipment that rotate relative to one another, such as slip rings, and cannot compensate for problems of cable twisting during and after mating.